For example, a storage system including an array of magnetic disks has a main unit and is connected to a plurality of internal units connected by an internal network inside the storage system. Each internal unit includes a control circuit controlling a magnetic disk. The main unit controlling the plurality of the internal units is connected to an external network including a monitoring terminal.
The main unit acquires information from the plurality of the internal units in the storage system and confirms the statuses of the internal units by communication by Ethernet® in the storage system. Furthermore, the main unit has to communicate with the monitoring terminal, i.e., a computer, outside of the storage system, so also communicates with the outside of the storage system by Ethernet®. For this reason, it is necessary to ensure that the Internet Protocol (IP) address of the main unit used in communication at the outside of the storage system and the IP addresses of the internal units at the inside of the storage system do not conflict.
In general, to avoid conflict of IP addresses, IP addresses in a network are dynamically assigned using the Dynamic Host Configuration Protocol (DHCP). When using the DHCP for network control in a storage system, each internal unit requests an IP address from the main unit and borrows an IP address with a time limit of use. However, the following problem arises when using the DHCP between the main unit and the internal units in the storage system.
The problem at the time of use of the DHCP is that even if the main unit wants to change an IP address of an internal unit lent by the main unit, it is not possible to immediately change it. The reason is that the main unit has to receive a lending request from the internal unit in order to change the IP address. That is, it is not possible to control an IP address in real time voluntarily from the main unit side. In other words, the main unit cannot change the IP address of an internal unit at any time and without receiving for a lending request from the internal unit.
If it is not possible to change the IP address of an internal unit of a storage system in real time, for example, it would not be possible to dynamically change the external use IP address of the main unit from the monitoring terminal at the outside of the storage system. This has the result of lowering the commercial value of the storage system. (For related art, see Japanese Laid-Open Patent Publication (A) No. 2002-190811.)